This invention relates to a method for hardfacing which is required to provide wear resistance for a mechanical seal ring or a roll etc. consisting of a ferrous base material. WC is generally used a method for hardfacing ferrous base materials. Various kinds of metal products are sprayed with WC by plasma spraying, wire explosion spraying, or a detonation gun process etc., and there is formed a hard metal coating on the surface of a metal product because WC has a high hardness. In this case, it is difficult to spray using only WC because of its high melting point, so that in most cases in which it is used, the material is bonded by WC powder and Co or Ni bonding materials. However, in the case of using Co or Ni to WC powder as the bonding material, it is difficult to avoid a considerable amount of pores on the sprayed coating even if it is used with various kinds of spraying methods. Also the adhesion strength for the base material is low, in the order of 400.about.800 Kg/cm.sup.2, therefore it is difficult to stand up in use under the condition of high loading, and there are further defects in that it causes cracking. Accordingly, a composite powder consisting of WC and Ni-P alloy was developed in Japan and applied for the purpose of overcoming the above-mentioned defects (Japanese Patent Application No. 55602 of 1980).
In the case of utilizing a sprayed coating using the composite spraying powder of WC and Ni-P alloy by plasma spraying, the porosity of the sprayed coating is less than 1% and the adhesion strength for the ferrous base material may obtain a strength of more than 800 Kg/cm.sup.2. However, the requirement of a coating which has high-density and high strength practicality is still not satisfied. Alternatively, Japanese Patent Publication No. 42854 of 1979 describes a method for the material bonding of WC powder with Co or Ni which has also the above-mentioned defects. This Japanese Pat. No. 42854 is a method for hardfacing by mechanically mixing WC powder with Ni-P alloy powder, spraying it on the surface of a base material, and heating the sprayed base material. In this method, WC is a carbide of high melting point and Ni-P alloy is a soldering material of low melting point. The defects in this method are that Ni-P is on alloy of low melting point and therefore is preferentially sprayed and adheres easily, and WC powder has a high specific gravity so that it sediments easily. Therefore, during the mixture of WC powder and Ni-P alloy, the powder remains in the container of the spraying apparatus, and the mixture becomes nonuniform. For these reasons, there are defects that occur with the usage of this patent, which include: the structure of a sprayed coating has the tendency to become non-uniform, and the spray coating may become porous even after heating if the grain boundaries of a sprayed particle have a lot of crevices.